KR100221098B1 - Process to produce sanitary napkins with low tolerance between crimped side seal and absorbent core - Google Patents

Abstract

The invention relates to a process for making a sanitary napkin having an absorbent core between a topsheet and a backsheet and a crimped side seal combining the topsheet and the backsheet around the core. In particular the process relates to making a product which has a small or no distance between the core and the crimped side seal of a sanitary napkin, by calandering the core to its final shape after the sides have been sealed together.

Description

Method of making sanitary napkins with small gaps between corrugated side seals and absorbent cores

In the past, the spacing between the core edge and the side seals was very large to accommodate changes caused by core growth during, for example, calendaring of the core prior to crimping, generally 10 Or less. The newly devised method used a series of calendering steps to reduce this change, thus bringing the core edge and side seal closer. The calendaring step after the formation of the side seals has made it possible to make sanitary napkins with little or even no gap between the core edge and the corrugated side seals.

The absorbent article generally consists of three layers: a liquid impermeable back sheet, a liquid permeable top sheet, and an absorbent core located between the back sheet and the top sheet. It is common to have an endless back sheet roll material and a top sheet roll material introduced from above and below the discontinuous absorbent core structure when the details are joined together during the manufacture of the absorbent article.

The top sheet and back sheet are bonded to the cores at regular intervals from each other to accommodate changes in core size due to the changes introduced when the core is made. The bond can be continuous or discontinuous. The spacing must also accommodate the change in arrangement between the core and the coupling equipment. The resulting product thus had a constant gap between the innermost line of the edge of the bond between the top sheet and the back sheet and the edge of the core. Commercial pleat seals, in particular, do not allow gaps between the core edge and the pleat seals because the foreign material between the top sheet and the back sheet does not break or even form the pleat seal.

US Pat. No. 4,592,708 describes the problem of the gap between the core edge and the side seal edge and the edge limit of the core. To overcome this problem, the patent suggested calendaring the absorbent core in two steps before joining the top sheet and back sheet by crimping. The U.S. patent therefore describes an improvement step in the context of the present invention, but does not satisfy the requirement of making the gap between the absorbent core edge and the joining edge almost unrecognizable.

In connection with this problem, US Pat. No. 4,888,231 and European Patent Application No. 429393 describe a special method of calendaring absorbent cores and joining the back sheet and the top sheet around these cores. However, neither of these documents provides a solution provided by the present invention.

The present invention relates to a method of making a sanitary napkin having an absorbent core between a top sheet and a back sheet and a corrugated side seal that joins the top sheet and the back sheet around the core. In particular, the present invention relates to a method of making a product having a small gap between the pleated side seal of the sanitary napkin and the absorbent core.

It is an object of the present invention to have a pleated side seal between an upper sheet and a back sheet, and having an absorbent core structure positioned therebetween, with the intention of eliminating the gap between the lateral seal and the absorbent core 6 It is to provide a method for producing an absorbent product, in particular a sanitary napkin, which is minimized at less intervals.

Yet another object of the present invention is to provide a method that does not use additional or new equipment as compared to current commercially available products.

Another object of the present invention is to provide a method for an absorbent structure having a profile with varying amounts of absorbent material in different absorbent structure portions, in particular with more absorbent material in the center of the absorbent structure. . Ideally, this combines with calendaring to produce an absorbent structure of uniform density despite the profile. This is accomplished by so-called profile calendaring using a profiling roll calendar.

The present invention relates to a method of making a profiled disposable absorbent article having a first sheet, a second sheet and a fibrous core. The core is located between the first and second sheets, the two sheets joining each other along a continuous or discontinuous line. This way,

a) 3-8 at least partially along the line connecting the circumference of the core Bonding the first sheet to the second sheet at intervals from the core of;

b) calendering the cores between the sheets to approximately uniform density in the calender, the calendering extending the interval of step a) by stretching the core along its circumference, preferably 1 Shorten by the above.

Most preferably, the spacing between the core and the joining line after the calendering step is 2 Shorten by more than 0 It is best to shorten it at intervals.

In general, they should be joined along an endless line connecting all the perimeters of the absorbent core. Preferably, the bond is provided by a crimping method.

A separate calendaring step can be included before the joining. If an absorbent core is formed on a laydown drum with pockets, a preliminary calendar on the drum as described, for example, in US Pat. No. 4,592,708 or 4859388 to further shorten the spacing between the joining line and the core. Rings may be included.

In the following the invention is described with reference to a sanitary napkin as an absorbent article. However, other absorbent articles such as baby diapers, adult incontinence products and the like can also be produced by the method according to the invention.

The design of sanitary napkins and materials used in such preparations is well known in the art. For example, European Patent Applications (EPA) 134086, 130848, 335253, 336578, WO 93/01783, and pending US patent applications filed on February 4, 1994. No. 08/192240.

In general, the sanitary napkin optionally includes an absorbent core made of a fibrous material that further includes absorbent hydrogel particles. The sanitary napkin core is manufactured by the laydown method as an embodiment described in US Pat. No. 4,592,708 or 4859388. However, other methods of making fibrous absorbent cores may also be used in accordance with the present invention. Preferably the absorbent core is profiled to distribute an increased amount of absorbent material towards the center relative to the circumference of the core.

Once these absorbent cores are manufactured they are placed continuously on the conveyor belt in a spaced apart manner. These cores are positioned between the top sheet and the back sheet by receiving each roll material receptively from above and below to form an endless band of absorbent article. The two sheets then join each other around the perimeter of the absorbent core.

The binding can be provided by a commercially available method in the art of making absorbent articles. In the case of sanitary napkins, crimping is often used because crimping forms a relatively tight seal between the top sheet and the back sheet that circumscribes the absorbent core. Crimping also does not require additional materials such as adhesives.

In the present invention, there is provided a calendering step of joining the top sheet to the back sheet and then elongating the absorbent core to match its circumference to coincide with the joining line between the back sheet and the top sheet.

In order to protect the corrugated seal between the back sheet and the top sheet, it is necessary to use profiling calendering, a calender roll with material distribution of the absorbent core such that heterogeneous elongation around the core is minimized. Generally, the profiling of the calendar is followed by the profiling of the absorbent material distribution of the core. This achieves uniform elongation and prevents the separation of corrugated seals therein. Profiled calendaring may be provided by a single profile roll calendar or a dual calendar system, where the first calendar of the dual calendar system is more widely spaced apart from the profiled roll, and the second calendar is more narrowly spaced apart.

Also, although not preferred, a calendering step of the absorbent core may be included prior to sealing between the back sheet and the top sheet. Such calendaring can be profiled but is not necessary.

Preference is given to using a laydown drum calendering process as described in US Pat. Nos. 4,592,708 and 4859388 in combination with the present invention.

The process flow diagram of the prior art and the process flow diagram of the present invention are described below in comparison. Sanitary napkins with a core of fibrous cellulose (also referred to as airfelt in the above cited art) and absorbent hydrogel particles can be prepared by this process. The fibrous airfelt is generally carried on the laydown drum where the absorbent hydrogel particles are mixed by the air stream to form a uniform mixture formed of the absorbent core of the laydown section.

Thereafter, the absorbent core has a calculated absorbent core of 56 Width and 30 Calendar on a laydown drum in accordance with US Pat. No. 4,592,708 or 4859388. These cores are placed on the conveyor belt and spaced apart in discontinuous order by the use of a second conveyor belt with increased speed.

The core is conveyed to the first calender by the conveyor belt. According to the prior art process, the thickness is 10 By the lateral elongation of the absorbent core being shortened to 64 Create a product with a width of. According to an embodiment of the present invention, no calendaring is performed at this stage.

The absorbent article is combined at the crimp section with the top sheet and the back sheet provided respectively below and above the absorbent core. Because of process variations, the spacing between the inner edge and the core in the corrugated seal on the longitudinal side of the sanitary napkin is 5 on each side in the prior art process. 2 in each aspect in the process according to the invention to be. 5 3 of Is believed to be caused by the calendar before crimping.

This means that in the prior art products the spacing between the inner edges of the corrugated seal is 58 +2 5 = 68 Results in. However, according to the present invention, because of the smaller core width and shortened change before crimping, +2 2 = 60 Needs an interval.

The process according to the invention then replaces the absorbent core. On each side between the corrugated seal and the absorbent core, extending to the total width of 1 While leaving the thickness of the absorbent core as in the prior art 10 It has a second calendaring step to shorten.

The process according to the invention allows the use of lower web widths of the top sheet and back sheet than in the prior art processes. Depending on the particular absorbent product, in addition to product improvements such as absorbent core coalescence and aesthetic appearance, it reduces the consumption of raw raw materials for all product width dependent components up to 20%.

[Process Flow Chart of Example]

Claims (8)

A method of making a disposable absorbent article comprising a first sheet, a second sheet, and a fibrous core positioned between the first sheet and the second sheet, the method comprising: a) at least partially with respect to the fibrous core along the perimeter of the fibrous core; 3 To 8 Bonding the first sheet to the second sheet at an interval of b, and b) spacing the fibrous core between the sheets in a profiling calendar to stretch the fibrous core along its perimeter Shortening the process. The method of claim 1, wherein in step b) the spacing for the fibrous core is 1 How to shorten it. The process of claim 2, wherein in step b) the spacing for the fibrous core is 2 How to shorten it. The profiled roll calender according to claim 1, wherein the core is profiled to have an increased absorbent material content towards the core center and the profiling calendar of step b) is suitable for profiling the core. Is a dual calendar system. The method of claim 1, wherein the sheet is joined along the entire circumference of the core. The method of claim 1, wherein the bonding of step a) is provided by crimping. The method of claim 1, further comprising forming the core on a profiled laydown drum and precalendering the core on the drum. The method according to claim 1, wherein the absorbent product is a sanitary napkin.